1. Technical Field
This disclosure generally relates to emergency vehicles, and more particularly relates to ambulances.
2. Background Art
Ambulances have been used from the days of horse-drawn carriages. When an injured person is being transported in an ambulance, any bump or jolt can cause pain. Thus, the need to cushion the ride of a patient in an ambulance is a long-recognized need. For example, U.S. Pat. No. 42,152 issued on Apr. 5, 1864 to Arnold discloses an ambulance that includes a couch that yields or gives vertically under the jarring movement of the ambulance. Many other devices and systems have been developed over the years to give a patient a more comfortable ride in an ambulance.
U.S. Pat. Nos. 6,890,137 and 7,621,705 to Hillberry et al. disclose a system for supporting an ambulance cot that includes vibration reduction devices upon which the wheels of an ambulance cot may be placed. The vibration reduction devices are supported by springs, which cushion the ambulance cot to provide a smoother ride for the patient on the cot. The use of springs makes the Hillberry system unsuitable for different patients with a wide variance of weight. For example, if the springs are selected to provide a comfortable ride for a heavy patient, the same springs will provide a very stiff ride to a much lighter patient. If the springs are selected to provide a comfortable ride for a light patient, the springs could bottom out for a heavy patient. Given the wide range of weights of patients transported by ambulances, the spring-based system in the Hillberry patents does not provide the needed range of function as weights vary.
U.S. Patent Application Publication No. 2013/0133317 to Zumbrum discloses an ambulance shock absorbing system includes gas actuators mounted to an ambulance floor, and a stage mounted atop the gas actuators. The Zumbrum system includes limit switches that define two positions of the stage based on the state of the gas actuators. To raise the stage in Zumbrum from its lower position, a valve is opened and gas inflates the gas actuators until the gas actuators raise the stage to a position until the upper limit switch is activated, which causes the valve to close, thereby keeping the stage at its upper position defined by the upper limit switch. To lower the stage in Zumbrum from its upper position, the valve is opened, allowing the gas in the gas actuators to exhaust out, thereby lowering the stage until it contacts the lower limit switch, at which point the valve is closed, thereby keeping the stage at its lower position defined by the lower limit switch.
The Zumbrum system only has two positions for the stage, an upper position and a lower position. This means when a patient is being transported, the stage is moved to its upper position. The one upper position in Zumbrum does not accommodate patients whose weights vary widely. In addition, the Zumbrum system does not include many desirable features.